The clip fasteners of the general type with which we are concerned here are often used to attach moldings, trim pieces or other such components to panels and other such members. They are also used to secure connecting terminals to work pieces of one kind or another. In many cases, the fasteners are formed with retaining tabs or lugs which are sheared from spring-like legs so that when the fastener legs are received in a work piece opening, the tabs resiliently engage the edges of the opening to retain the fastener in place. A screw extending through a second work piece is turned down through an aperture in the fastener to mechanically connect the two work pieces. Such fasteners are described, for example, in U.S. Pat. Nos. 3,486,158 and 3,795,890.
Heretofore, clip fasteners of this general type have been intended for securement to relatively rigid work pieces or members made of metal, stiff plastic or other hard material. Furthermore, in order to prevent the fastener from turning relative to the work piece, the work piece opening receiving the fastener is made rectangular or given some other irregular shape or the fastener and work piece are provided with abutting shoulders. However, of late, fastener-receiving work pieces made of softer materials such as fiberglass mat sheet molded compounds or so-called SMC materials have come into widespread use particularly in the automotive and boating industries. For example, automobile instrument panels and dashboards as well as boat hulls are fabricated of such materials.
When molding members of this sheet molded mat material, there is relatively poor control over the thickness of the finished parts. Furthermore, when fastener openings are formed in the parts, it has been found that the molds do not core all of the openings completely. Therefore, when the time comes to install fasteners in such openings, the operator often has to take time to remove uncored material from those holes before he can install the fasteners. With this in mind, it can be appreciated that if the opening is round, a standard drill and bit can be used to perform that operation very quickly. On the other hand, if the holes are not round, a special tool must be employed to cut or saw the excess material from each hole. Needless to say, that is a much more time-consuming task than a simple drilling operation. Therefore, prior fasteners such as the ones disclosed in the above named patents are not particularly suited for installation in sheet-molded fiberglass automotive or boating parts of the type described here.
Further it should be appreciated that when the fastener receiving holes in such parts are finish-formed by hand by different operators, there is bound to be some variance in the size of the holes. Therefore, it is essential that the fasteners installed in such parts be capable of tolerating some variation in the size of the opening in which it seats as well as in the thickness of the part itself.
Finally, many prior snap fasteners of this general type utilize a relatively large amount of material and they may require several different stamping operations in order to form them. Considering the very large numbers of such fasteners that are used in industry today, it would be highly desirable from a cost standpoint to provide such a fastener which can be fabricated in a few steps using a minimum amount of material.